A philosopher who embarks on an examination of war risks stepping into a long intellectual journey that requires continued thought and elaboration. This is true regardless of the internal logical validity of a proposed explanation. In the case of a discussion about war, it is particularly important to go beyond proffered definitions and explanations in order to consider the broader philosophical problems they often mask.

The question of war evokes intense debate among scholars, historians and philosophers. Nevertheless, there are some essential continuities in the concept of war that should be acknowledged. First and foremost, war is a conflict between states or states-like entities that are capable of exercising coercive force. This is a feature that distinguishes it from other forms of human conflict such as terrorist or insurgent activity, civil war or revolution, and even from the violence associated with interspecies confrontations.

Moreover, wars are typically fought over resources or territories, resulting in the displacement of populations. This has serious consequences for all those involved, from combatants to civilians, including children. It also poses a major threat to people’s ability to function at work and at home. This can contribute to mental health issues like depression and anxiety, and lead to a range of other problems such as poverty and homelessness.

Another enduring aspect of war is that it is often chaotic and unpredictable. Despite the efforts of planners, there are always unanticipated developments. New technologies may fail to deliver on their promise, unforeseen weather conditions can affect operations, or even a simple misunderstanding between adversaries can lead to escalating tensions. In these situations, leaders may be forced to reassess their options. They may suffer doubts, or they might cling to a stubborn faith that the fortunes will change.

Finally, the concept of war is also a contest between competing values. This is a contest that can be won or lost depending on the balance of power between opposing forces, but it also depends on the strength and stability of the state system itself, as well as the cultural environment within which that state operates.

All of this means that the definition of war is a complex and evolving one. It has many facets that are influenced by historical and cultural factors, such as fear and honour, survival and the need for power, enmity and passion, chance events and friction, rationalised political objectives, dynamic interaction and unpredictability. This explains why there is no single agreed definition of war and why it has a long history of being a controversial subject. However, it is important to recognise that even a war that is resolved has a legacy that makes future conflict more likely. Unless the causes of war are addressed, there is little hope for preventing future conflicts and violence between humans.